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The Hunga Tonga-Hunga Ha’apai eruption lasted less than a day, but released the most water vapor into the atmosphere from a volcano on record. Researchers say the blast could temporarily warm surface temperatures in the coming years and also destroy stratospheric ozone.
On January 15, the underwater volcano erupted and sent a shock wave that reverberated around the world. The powerful blast spewed aerosols, gas, steam and ash 36 miles high, possibly the tallest volcanic plume in the satellite record. The explosion damaged more than 100 homes and killed at least three people on the island of Tonga. A new study also shows that the volcano released an unprecedented amount of water vapor, a powerful greenhouse gas that traps heat on Earth.
NASA satellite data show the volcano shot more than 146 teragrams of water — enough to fill 58,000 Olympic-sized swimming pools — into the second layer of Earth’s atmosphere, known as the stratosphere, where the ozone layer sits and just above it airplanes fly. The study states that the amount released is equivalent to 10 percent of the water already in the stratosphere.
“This is the first time this type of injection has happened in the entire satellite era,” which includes water vapor data since 1995, said Louis Millan, the study’s lead author and a NASA atmospheric scientist. “We’ve never seen anything like this before, so it was pretty impressive.”
Volcanic eruptions eject many different types of gases and particles. Most eruptions, including Hunga Tonga, release particles that cool the Earth’s surface by reflecting sunlight back into space, but these typically dissipate after two to three years. However, very few blow water vapor that high. This water vapor can stay longer in the atmosphere – five to 10 years – and trap heat at the Earth’s surface.
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Millán speculates that the water vapor could begin to have a warming effect on the planet’s surface temperature once the accompanying cooling particles dissipate in about three years. He is not sure how much the temperature will rise, as it depends on how the water vapor jet develops. The team suspects the increased warming will continue for several years until circulation patterns in the stratosphere wash the water vapor into the troposphere, the layer where Earth’s weather happens.
“This is just a temporary warming and then it will go back to what it was supposed to go back to,” Milan said. “It won’t make climate change worse.”
NASA atmospheric scientist Ryan Kramer added that given the multiple factors that cause temperature changes on timescales of years, the warming effect from the volcano could also be lost in the noise, depending on its magnitude.
On a shorter one on a time scale, increased water vapor may also exacerbate stratospheric ozone depletion, said Susan Strahan, an atmospheric chemist at the University of Maryland Baltimore County and NASA.
Stratospheric ozone protects the Earth’s surface from harmful ultraviolet radiation. Ozone-depleting chemicals were largely phased out through the 1987 Montreal Protocol and subsequent amendments.
Strahan, who was not involved in the research, explained that the excess water vapor would affect many chemical reactions that control stratospheric ozone concentrations. NASA satellite data in July already show a decrease in ozone levels compared to previous years in the area where the excess water vapor is most concentrated. She added that a full analysis should be done to determine the cause.
“Right now there are probably impacts, but what we need [is] a model to tell us is by what mechanism(s) the impacts occurred. Almost certainly, meteorology and chemistry will play a role – the questions are how much, where, when?” Strahan said in an email.
Strahan also said that the excess water vapor could enhance the formation of special nocturnal clouds that appear as shimmering wisps of ghosts in the night sky. They occur about 50 miles into the atmosphere, higher than the stratosphere, and are some of the rarest, driest, and highest clouds on Earth. For many people, clouds provide remarkable viewing of the sky. However, the researchers believe that any noticeable change in these clouds will not appear until later, depending on how long it takes for the water vapor to travel up into the atmosphere where the clouds form.
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Overall, Millán said excess water vapor isn’t anything to worry about per se, but “something that’s just interesting that happens.” He and his colleagues are taking this opportunity to test their computer models that help us understand climate change and weather forecasting in general.
“We have these huge amounts of water vapor moving in the stratosphere, and we can test how well the models reflect its movements in the atmosphere,” Millan said. “This volcano will give a lot of work to many researchers.”
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